A slave dealt harshly with his master, so he (i.e. the master) said: Indeed as you can see I exercise patience with this boy in order to train my soul. (That is) because if I exercise patience with the slave (whilst bearing) that which is hated, I will exercise more patience with other than him (i.e. when dealing with others).

[Source: Kitaab Uyoounul Akhbaar’ of Ibn Qutaybah (rahimahullaah): Vol: 1-page: 332]